How to change value of object data property by using python script?
Assuming you want to add extrude/bevel to you Curve object :

Select your curves and run:

import bpy

obs = bpy.context.selected_objects

for ob in obs:
    if ob.type == 'CURVE':
        curve = ob.data
        curve.dimensions = "2D"
        curve.offset = 0            # set offset value
        curve.extrude = 0           # set extrude value
        curve.bevel_depth = 0       # set bevel depth value
        curve.bevel_resolution = 0  # set bevel resolution